Bangkok, Thailand (CNN) -- An accused international arms dealer known as "The Merchant of Death" was extradited to the United States on terrorism charges Tuesday, Thai police said.

Viktor Bout left Thailand on a U.S.-chartered jet, said police Col. Supisarn Bhakdinarunart, chief of the Crime Suppression Bureau.

The chief said agents of the U.S. Drug Enforcement Administration escorted Bout, who is a Russian citizen and former Soviet military officer.

The Russian government issued a stiff reaction, blaming the "unprecedented political pressure" by the United States on the Thai courts for what it called an "illegal extradition."

"This is an example of an outrageous injustice," said Russian Foreign Minister Sergey Lavrov in comments to reporters in Nairobi, Kenya. "We as a country will continue assisting Viktor Bout as a Russian citizen in every possible way."

The plane left about 1:30 p.m. Tuesday, after Thai Prime Minister Abhisit Vejjajiva cleared the last obstacle for Bout's extradition.

Bout has been indicted in the United States on a series of charges, including counts of illegally purchasing U.S. cargo planes to ferry weapons to warring parties and regimes in Africa and the Middle East.

He was arrested in Bangkok in March 2008. DEA agents led a sting operation by posing as members of the Revolutionary Armed Forces of Colombia (FARC). Bout had been in Thai custody since.

Russia's Foreign Ministry, in a statement on its website, said the extradition occurred despite two Thai court decisions "that found Bout's guilt unproven" and said the move has no "rational explanation and justification" legally.

"There are no doubts that the illegal extradition of Viktor Bout is a result of an unprecedented political pressure applied on the Thai court and government by the United States. All this can be characterized as the [American] intervention in the judicial system and puts in question the independence of the Thai legal system and the decisions made by the Thai government," the ministry said.

"It is very deplorable that the Thai government succumbed to the outside pressure and conducted the illegal extradition of Viktor Bout," the ministry said.

Bout has repeatedly said he has broken no law and that the allegations against him are lies.

He is accused of supplying weapons to war zones around the world, from Sierra Leone to Afghanistan.

The United States has charged Bout with agreeing to sell surface-to-air missiles, armor-piercing rocket launchers, "ultralight" airplanes, unmanned aerial vehicles and other weapons to the FARC.

U.S. authorities accuse Bout of four terrorism offenses: conspiracy to kill U.S. nationals, conspiracy to kill U.S. officers or employees, conspiracy to acquire and use an anti-aircraft missile, and conspiracy to provide material support or resources to a designated foreign terrorist organization -- a designation given to the FARC by the U.S. State Department.

Bout allegedly began building his arms business as the Soviet Union disintegrated in the early 1990s. He acquired surplus Soviet planes and started shipping arms and ammunition to conflict zones, according to the U.S. Treasury Department.